Sordaria Lab

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Sordaria Lab
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Lab 3 Mitosis Meiosis

• Exercise 3B
• Studies crossing over and recombination during
  meiosis using asci from crosses between wild and
  mutants spores in the fungus Sordaria fimicola.
• Arrangements will be used to estimate the
  percentage of crossing over that occurs.

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Lab Objectives

• You should be able to
• Calculate the map distance of a particular gene
  from a chromosome's center for between two genes
  using an organism of your choice in a controlled
  experiment
• Demonstrate the role of meiosis in the formation
  of gametes using an organism of your choice, in a
  controlled experiment

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Class Ascomycetes (Cup Fungi)

• Largest division of fungi, terrestrial
• All produce spores in pouch-like asci

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Crossing over
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Non-Crossing over
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Crossing over
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Innoculating the Plate
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Counting the Asci

• Always 8 spores in each Asci (also called
  conidia)
• Used in genetic recombination studies

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showing crossing-over?
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showing crossing-over?
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showing crossing-over?
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showing crossing-over?
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showing crossing-over?
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showing crossing-over?
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showing crossing-over?
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showing crossing-over?
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showing crossing-over?
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Calculate the Map Units

• Calculate the percent of crossovers by dividing
  the number of crossover asci (2222 or 242)
  by the total number of asci x 100.
• Calculate the map distance, divide the percent of
  crossover asci by 2.
• of crossover asci is divided by 2 because only
  half of the spores in each ascus are the result
  of crossing over.